The invention relates generally to fluid control valves for operating a fluid-actuating device and more particularly to either selector or primary fluid control valves employing one or more ball-poppets. Although the principles of the invention are applicable to both pneumatic and liquid fluid control valves, it is especially applicable to high-pressure pneumatic control valves, as well as to such pneumatic controls adopted for selective switching between two or more different outlet pressures.
A variety of fluid control valves, especially those of the pneumatic nature, have been provided for numerous high-pressure applications, including those used in processes for blow-molding plastic bottles or other such containers. Although such control valves have generally functioned satisfactorily for the processes to which they have been applied, they have been found to be subject to excessive wear due to the high working fluid pressures involved and thus have had a relatively short life span. In addition, also in part due to the high pressures of the actuating fluids, such previously-provided fluid control valves have been subject to an unacceptable level of internal working fluid leakage, such as cross-over leakage that occurs when opening a supply portion of the valve and closing an exhaust portion of the valve in order to admit working fluid to the fluid-actuating device. As a result, both of these factors have contributed to the high operation costs and high maintenance costs of the systems in which the previously-provided fluid control valves have been used.
In addition, many applications require the capability of selecting between two or more control valve outlet pressures, especially in pneumatic systems. One example of such an application is the above-mentioned processes for blow-molding plastic bottles or other such vessels or containers. In these exemplary processes, it is often desirable or necessary to initially admit a relatively lower pressure to the mold in order to introduce the plastic (or other material) into the mold cavity or cavities and then to admit a relatively higher pressure to force or expand the material into the desired shape dictated by the shape of the mold.
Therefore, the present invention seeks to provide an improved high-pressure or multi-pressure fluid control valve that is significantly less subject to wear and that substantially negates internal working fluid leakage, thus contributing to the long life of the fluid control valve and reducing both system operating and system maintenance costs. Furthermore the present invention also seeks to provide such a control valve capable of selectively delivering two or more different pressures to the process system.
In accordance with the present invention, a primary control valve for operating a fluid-actuated device preferably has an inlet in communication with a source of pressurized working fluid, an outlet passageway and port in fluid communication with the fluid-actuated device, and a fluid supply passage providing fluid communication for the working fluid from the inlet to the outlet. The control valve preferably includes a generally frusto-conical supply valve seat in the a fluid supply passage with the supply valve seat having a smaller-diameter downstream end and a larger-diameter upstream end. A generally spherical supply poppet or supply ball-poppet is selectively movable between respective supply closed and supply open positions, into and out of a substantially line-contact for sealing with the smaller-diameter end of the supply valve seat. The spherical supply ball-poppet has a chord dimension at such line-contact with the smaller diameter downstream end of the valve seat that is smaller than the larger-diameter upstream end of the supply valve seat. This arrangement can also be used in a pressure selector fluid control valve according to the present invention, as described below.
Each side of the preferred frusto-conical supply valve seat has a supply seat angle relative to the centerline of the supply valve seat that is greater than an angle formed by the centerline of the supply valve seat and a line tangent to the supply ball-poppet at the above-mentioned substantially line-contact when the supply ball-poppet is in its closed position. The included angular relationship of the valve seat angles on both sides of the centerline is preferably approximately ninety degrees. This results in a annular space being formed between the supply valve seat and the spherical supply ball-poppet, which defines a restricted supply flow area upstream of the above-mentioned substantially line-contact as the supply ball-poppet initially moves to its open position and as high-velocity and high-pressure working fluid initially flows downstream past the supply ball-poppet through the smaller-diameter end of the valve seat. This is greatly advantageous because any sonic flow erosion caused by the initial flow of the high velocity and high-pressure working fluid through the annular restricted supply flow area is thus shifted substantially immediately to an upstream surface of the supply valve seat that is adjacent to such annular restricted supply flow area. Most significantly, such upstream surface of the supply valve seat is an area that is not sealingly contacted by the supply ball-poppet. Therefore, this immediate shifting of the sonic damage-susceptible area substantially minimizes sonic erosion of the nearly xe2x80x9cknife-edgexe2x80x9d smaller-diameter downstream end of the supply valve seat that is substantially line-contacted by the supply ball-poppet. In control valves according to the present invention that have both supply valving and exhaust valving, a similar arrangement is preferably provided in the exhaust passage way in fluid communication for exhaust fluid between the load outlet passageway (and load outlet) and the exhaust outlet. As mentioned above, this arrangement is equally applicable to a pressure selector fluid control valve, as described below.
In addition, the present invention preferably includes a generally cylindrical cavity immediately upstream of the larger-diameter upstream ends of the supply and/or exhaust valve seats, with such cavity preferably being larger in diameter than the larger-diameter upstream end of the respective valve seats. A cylindrical poppet guide or ball-poppet guide is located in this enlarged-diameter cavity of the fluid passageway, with the ball-poppet guide having a central guide bore extending axially therethrough. A number of circumferentially spaced-apart axially-extending guide fins protrude radially inwardly into the guide bore, with the ball-poppet being received within the guide bore for axial movement within radially inward edges of the guide fins between its open and closed positions. The inner diameter of the above-mentioned cavity is preferably slightly greater than the outer diameter of the ball-poppet guide in order to allow the ball-poppet guide and the ball-poppet to float radially somewhat within the cavity. This allows the generally spherical ball-poppet to be substantially self-centering for sealing line-contact with the smaller-diameter end of the respective supply or exhaust valve seat. Such circumferentially spaced guide fins allow high pressure working fluid to flow therebetween, and the ball-poppet guide substantially minimizes wear on the ball-poppet and/or the valve seat that would result if it were to be allowed to rattle or otherwise move radially in the high-velocity fluid flow. Such a ball-poppet guide can also be used in a selector fluid control valve, as described below.
The present invention substantially also negates cross-over leakage in high-pressure fluid control valves having both supply and exhaust valving by energizing the exhaust ball-poppet actuator, thus closing the exhaust side of the control valve, just prior to energizing the supply ball-poppet actuator, which then opens the supply side and initiates supply flow to the load passageway and port.
The above-mentioned ball-poppets (for either primary or selector fluid control valves) are preferably composed of a metallic material, such as a stainless steel, for example, and the above-mentioned ball-poppet guides are preferably composed of a synthetic material, such as nylon, for example. Those skilled in the art will readily recognize that other metallic, synthetic, or non-synthetic materials can also be employed for the ball poppets and/or the ball-poppet guides, depending upon the particular working fluid (pneumatic or liquid) being employed, as well as the particular working fluid pressures involved, as well as depending upon the particular application in which the fluid control valve of the present invention is employed.
The present invention also provides a pressure selector fluid control valve for selectively supplying at least two different working fluid pressures to a fluid-actuated device, either directly or by way of a primary fluid control valve, such as that discussed above. An exemplary selector in fluid control valve according to the present invention preferably has a high-pressure inlet in fluid communication with a source of working fluid at a relatively high pressure, a low-pressure inlet in fluid communication with a source of working fluid at a relatively low pressure, and a load fluid outlet passageway interconnected in fluid communication with the fluid-actuated device or primary fluid control valve inlet. Such a selector fluid control valve further includes a normally closed high-pressure valve mechanism in fluid communication between the high-pressure inlet and the load fluid outlet passageway to selectively allow high-pressure fluid flow from the high-pressure inlet to the load fluid outlet passageway, as well as a normally open low-pressure valve mechanism in fluid communication between the low-pressure inlet and the load fluid outlet passageway to selectively allow low-pressure fluid flow from the low-pressure inlet to the load fluid outlet passageway. A pilot actuator is provided and is selectively operable to force the normally closed high-pressure valve mechanism into an open position and allow said high-pressure fluid flow from the high-pressure inlet to the load fluid outlet passageway. This high-pressure fluid being admitted into the load fluid outlet passageway forces the normally open low-pressure valve mechanism into a closed position to prevent fluid flow between the low-pressure inlet and the load fluid outlet passageway. Thus the selective actuation or energization of the pilot actuator, either the high-pressure or low-pressure working fluid (such as a pneumatic working fluid, for example) can be admitted to the inlet of a fluid-actuated device or the inlet of a primary fluid control valve, such as that described above or of virtually any type.
At least one or preferably both of the above-discussed high-pressure and low-pressure valve mechanisms can include a generally frusto-conical valve seat located in a valve fluid passageway in fluid communication with the load fluid outlet passageway, with the valve seat having a smaller-diameter downstream end and a larger-diameter upstream end. A generally spherical ball-poppet is selectively movable between respective closed and open positions into and out of substantially ball-poppet line-contact for sealing with said smaller-diameter end of the supply valve seat. The generally spherical ball-poppet preferably has a chord dimension at said line-contact with the smaller-diameter downstream end of the valve seat that is smaller than the larger-diameter upstream end of the valve seat. The generally frusto-conical valve seat preferably has a seat angle relative to the centerline of the supply valve seat that is greater than an angle formed by the centerline of the valve seat and a line tangent to the spherical ball-poppet at the ball-poppet line-contact when the ball-poppet is in said closed position, with such seat angle preferably being approximately forty-five degrees such that the overall seat angle between diametrically opposite portions of the valve seat is approximately ninety degrees. An annular space formed between the valve seat and the spherical ball-poppet thus defines a restricted flow area upstream of the ball-poppet line-contact between the spherical ball-poppet and the smaller-diameter downstream end of the valve seat as the spherical ball-poppet initially moves out of said line-contact to its open position and as the working fluid initially flows downstream past the ball-poppet through the smaller-diameter end of said valve seat. By such an arrangement, any sonic flow erosion caused by the initial working fluid flow past the opening ball-poppet is shifted substantially immediately to an upstream area of the valve seat that is adjacent the restricted flow area and that is not sealingly contacted by the spherical ball-poppet. This substantially minimizes sonic damage to the smaller-diameter downstream end of said valve seat against which the ball-poppet is sealingly engaged when in its closed position. This greatly increases the life of the control valve by minimizing the wear on the sealing portion of the valve seat.
One or both of the fluid valve passageways can include a generally cylindrical cavity immediately upstream of the larger-diameter upstream end of the valve seat, the cavity being larger in diameter than the larger-diameter upstream end. The valve mechanism preferably includes a generally cylindrical ball-poppet guide located in the cavity of said fluid passageway, with the ball-poppet guide having a central guide bore extending axially therethrough. The ball-poppet guide preferably has a number of circumferentially spaced-apart axially-extending guide fins protruding radially inwardly into the guide bore, with the ball-poppet being received within the guide bore for axial movement within radially inward edges of the guide fins between its open and closed positions. The inner diameter of the cavity is greater than the outer diameter of the ball-poppet guide in order to allow the ball-poppet guide to float radially within the cavity and to allow the spherical ball-poppet to be substantially self-centering for sealing line-contact with the smaller-diameter end of said frusto-conical valve seat.
In any of the primary or pressure selector fluid control valves according to the present invention, the frusto-conical valve seat can alternatively be located in a replaceable valve seat disc that is of a harder material than that of the valve body.
Additional objects, advantages, and features of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings.